Aluminum air pipes

Drained: Homeowner’s plumbing pickle demands a lesson on vent pipes | Seattle Times

I recently helped a landlord in Pittsburgh. His wife had decided it was time to rip out an outdated platform bath. She wanted to replace it with a sleek new tub in the shape of an elongated basin. I have to admit that these tubs look great and they are also very comfortable.

However, after removing the tub and its platform, it became apparent to my reader that the plumber who installed the tub platform took a shortcut and installed the vent pipe required for the drain line of the tub above the bathroom subfloor. There was sufficient space to do this under the platform and the installation met code requirements.

However, the owner wasn’t sure what he could do to move the drain line. Fortunately, he provided me with photos which made it easier to troubleshoot his problem. I described how he could move the vent pipe so it was no longer above ground and still be up to code and work properly.

His dilemma is a reminder that more homeowners need to understand the importance of plumbing vent pipes. These pipes provide the path for air to follow when you flush the toilet, use a washing machine, or brush your teeth.

Before you turn on a faucet, the only water in your home’s plumbing pipes sleeps in a P-trap located under a fixture or floor drain. This water forms a barrier that prevents vermin and sewer gases from entering your home. When there is no water flowing, the drain pipes and vent pipes are simply filled with air or a mixture of air and sewer gas.

As soon as you flush the toilet or run water from a fixture, you are introducing water into the drainpipes. This water displaces the air and pushes it down the drain pipes in the same way a snowplow pushes snow. The air needs to be replaced immediately – and this happens via air being sucked in through one or more pipes protruding from your roof.

If enough water is moving fast enough through the plumbing drains and the vent pipes are clogged or missing, a vacuum will form and the necessary air will enter the system through one of the plumbing P-traps. You may have heard a sucking sound coming from a tub or sink when you flushed a nearby toilet or a washing machine started pumping water into the bathroom. system. These noises are the sounds of air entering the system. This is not a good thing, because the P-traps then lose their ability to repel sewer gases and vermin. To maintain adequate ventilation, there should always be an open path between each fixture and the roof.

So how can you make sure your vent pipes are in good shape? I prefer venting plumbing fixtures with pipes that interconnect and eventually exit through the roof.

You can have multiple vent pipes running through the roof to save on pipe material. It’s also easy to flash vent pipes so you never have a roof leak. I prefer to use a flashing boot made by Lifetime Tool which has a powder coated metal base and a special silicone rubber boot which is superior to the regular rubber boot flashings used by most plumbers.

Every few years, assuming you can safely climb onto your roof, you should install a garden hose in the roof vent pipe and run water through the pipe for a few minutes to clear the accumulated dust, tree debris or even bird droppings.

If you do this, assign sentries around the house to spot leaks. Although rare, it is possible for a vent pipe in an attic or wall to have a crack or a poorly sealed fitting. It may not be a problem for the air, but it becomes a big problem when gallons of water go through the vent pipes.

Place someone near the hose tap who can shut off the water immediately if a leak appears. You will benefit from discovering this leak, as this could be the reason why you notice the smell of sewer gas from time to time.

Tim Carter has worked as a home improvement professional for over 30 years. To submit a question or to learn more, visit